1. Field of Invention
This invention relates to a brake assembly including a hub and rotor. The brake assembly is particularly suited for application in a commercial vehicle.
2. Description of Related Art
Prior brake designs use a rotor fixed to a brake hub with fasteners or an integrated hub and rotor design. However, as the rotor is conventionally fixed with respect to the hub, the rotor must be carefully balanced to avoid uneven wear and compromised performance. Also, during braking, the rotor in such an assembly is subjected to high frictional forces that generate heat in the rotor causing thermal expansion/distortion, temperature variation across the face of the rotor, and heat transfer to the adjacent components including the hub and the fasteners. This is especially apparent in an integrated hub and rotor design.
When the rotor is fixed with respect to the hub, thermal expansion of the rotor is very limited because of the integral connection between the rotor and the hub. This creates thermal coning in the rotor surface and a large thermal gradient, which will induce high thermal stress leading to thermal cracking. The high thermal gradient generated during braking and the effects of the thermal expansion/distortion can cause vibration and thermal judder across the brake surfaces, resulting in a rough or irregular braking sensation. The high thermal stress and thermal distortion also reduce the life and performance of the rotor and increase maintenance costs.
Another problem associated with rotors connected to a hub, for example, a hat rotor that bolts onto a hub, is compound run-out. Referring to FIG. 13, this phenomenon is caused when a rotor surface 76, which is not perfectly flat or parallel due to inherent imperfections created during manufacturing, is connected to a hub 72, and the axes of rotation of the rotor 78 and the hub 72 are not in precise alignment. The potential run-out area in FIG. 13 is shown at 70. Misalignment results in poor rotor performance and durability.
Particularly in commercial braking applications, braking performance is especially stringent and closely monitored. It is important in such applications to provide a braking assembly that provides enhanced performance at low maintenance and replacement costs.